JP2001069087A - Addition and erasion arrangement, addition and erasion method and communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce optical loss and expenditure in addition/erasion by combining the addition/erasion of the optical channel in a wavelength division multiplex ring network with a wide band optical coupler and a wavelength converting and suppressing element. SOLUTION: Couplers 300A and 300B are respectively arranged in a working route and a protecting route and optical transmitters 315A and 315B for additionally supplying the optical channels of the prescribed wavelengths are connected to the respective couplers. The channel to be erased is supplied to an optical protecting and exchanging element 318, a selected signal is processed by tail end exchange, the selected optical channel is supplied to an optical receiver 320 and a component group required for removing traffic from a wavelength division multiplex(WDM) signal is expressed by the optical receiver 320 in terms of aggregation. A part of complex WPH signals λ1...λn including an additional optical channel λn+1 are supplied to optical fibers on the working route and the protecting route with outputs 305A and 305B and erased by the couplers 300A and 300B.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to optical communication networks and, more particularly, to signal insertion and deletion in wavelength division multiplexed ring networks.

[0002]

2. Description of the Related Art Optical fibers have been increasingly selected as transmission media for communication networks because of the advantages of high speed and bandwidth associated with optical transmission. Wavelength division multiplexing (WDM), which combines multiple optical channels with different wavelengths as a composite optical signal in a single optical fiber for the purpose of simultaneous transmission, is increasing speed and bandwidth for optical transmission applications. It has been used to meet requirements. With recent advances in optical network technology, system builders are attempting dense wavelength division multiplexing (DWDM), for example, to include 80 or more optical channels (ie, wavelengths) in a single fiber. Therefore, DWDM
Optical transmission technology is expected to revolutionize the telecommunications industry.

[0003] In view of the various advantages associated with the use of WDM and DWDM in long-haul transmission networks, W
DM and DWDM technologies are being considered for use in short-haul transmission markets such as intra-city networks. Conventionally, a short-haul transmission network is a synchronous optical network (SON) using time division multiplexing (TDM) or the like.
ET) has been implemented as a ring. This kind of SONE
Although T-rings have good performance, the strong and consistent requirements for bandwidth and its bandwidth management have exceeded the capabilities and capacity of SONET rings. As a result, there is a need for extending the enormous capacity and protocol independence of WDM and DWDM for these short-haul transmission networks at the lowest possible cost.

[0004] Specifically, there are many motivations for deploying WDM and DWDM in short-haul transmission networks to replace existing time division multiplexing systems. For example, high transmission efficiency can be achieved by directly deploying packet or cell-based transmission over individual optical channels. In addition, WDM and DWDM
The system provides more bandwidth and offers greater flexibility in managing dynamic bandwidth requests by today's users.

However, the implementation of WDM or DWDM in urban areas has its own problems compared to long-distance network applications. For example,
Add / remove requests are significantly larger when compared to long distance network applications. This is because urban area networks typically have users located much more densely in areas that are more topographically limited. In addition, traffic flows, diversity of traffic types, and dynamic changes in traffic levels as traffic is added and removed make traffic management in urban area networks more complex. Resolving this problem using prior art WDM and DWDM techniques similar to those used for long-distance network applications significantly increases cost and complexity in more cost-sensitive urban area environments.

For example, prior art approaches to optical add / drop multiplexing are usually based on the extraction of the total signal strength for a selected wavelength at the add / drop node. Components used for optical add / drop multiplexing include, for example, an in-line array wavelength grating router (AWG), fiber Bragg grating, or Mach-Zehnder (MZ).
F) Filters and the like are included. However, these devices have some disadvantages that are undesirable in practical applications in short-range applications such as ring networks. For example, their disadvantages include wavelength dependent loss; intensity loss and other transmission impairments due to bandwidth reduction and group rate dispersion; limited spectral bandwidth, poor scalability, and high implementation costs.

[0007]

In general, the economics of applying DWDM to office-to-office (IOF) and access city applications is the economics of optical multiplexer / demultiplexers, optical amplifiers, optical switches, and WDM sources. It depends very much on the cost of the optical components implemented at that time. Bandwidth flexibility is a key driver for these applications,
The cost of implementing these functions with the straightforward use of DWDM techniques is unacceptably high in these more cost-sensitive environments.

Thus, to realize the benefits of WDM or DWDM in an urban area network, a more cost-competitive and technically feasible solution for adding and removing optical signals is needed. ing.

[0009]

SUMMARY OF THE INVENTION Wavelength division multiplexing (WD)
M) The costs and optical losses involved in adding and removing optical channels consisting of WDM signals in a ring network are:
In accordance with the present invention, an add / drop arrangement utilizing a broadband optical coupler in combination with a wavelength conversion and suppression element is significantly reduced compared to the prior art. In WDM,
At each node with a broadband optical coupler-based add / drop element, a portion of the optical signal strength (ie, all optical channels) of the entire WDM signal is tapped off, and a single or multiple signals having a particular wavelength are removed. The channel is deleted at that node. The information (ie, data) to be added at that node is provided to the optical channel added to the WDM signal via the same wideband coupler. WDM (including all added optical channels)
Other parts of the signal's optical signal strength pass through that node on the WDM ring.

In accordance with another aspect of the present invention, at least one node in the WDM ring occurs as a result of recirculation of the optical channel in the WDM ring (ie, recirculation after the optical channel has passed its destination node). In order to reduce possible interference between optical channels, a wavelength conversion and suppression element is provided. Wavelength conversion and suppression may vary depending on the particular ring topology used with the broadband coupler-based add / drop arrangement. Add / drop arrangements in accordance with the principles of the present invention may be used in various ring architectures, including, but not limited to, path switching rings and line switching rings.

An add / drop arrangement in accordance with the principles of the present invention operates over a wide spectral range (ie, wideband) using components with low optical loss (ie, low loss in both the delete and pass paths), and It relies on techniques based on passive elements rather than techniques based on active elements, thus reducing cost and complexity as compared to prior art arrangements. Furthermore, the problems associated with the cascade arrangement of narrowband filters in the prior art add / drop arrangement are avoided by using a wideband coupler for adding and removing optical channels in a WDM ring.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS For a better understanding of the principles of the present invention, a typical example of a ring network will first be provided. Specifically, the light add / remove function,
An exemplary WDM ring including one or more network elements with optical add / drop multiplexers is described. For an overview of ring networks, including SONET / SDH rings and WDM rings, see Kamino
"Optical fiber communication" by v. et al. (Vol. IIIA, Volume 269-2)
75 and 567-573 (1997)). This document is a reference of the present invention. Note that while the principles of the present invention are described in the context of a single ring arrangement, the principles of the present invention are also applicable for multiple fiber overlays of survivable WDM rings, such as multiple ring architectures. I want to be. Further, while the embodiments described herein relate to a four-node network, the principles of the present invention are applicable to ring networks having any number of nodes. In this regard, the embodiments described herein are for illustrative purposes and do not limit the scope of the invention.

FIG. 1 illustrates a unidirectional path switching ring (UPSR) 100 including nodes 101-104 (labeled Node A through Node D, respectively) connected via optical fibers 110 and 111. Is shown. Nodes 101-104 are nodes 101 and 102
As illustrated in FIG.
11 for the signal transmitted via
Includes a network element with the ability to delete.
The basic principles of operation of a UPSR are known to those skilled in the art. For example, UPSR networks are known in the SONET / SDH domain. For example, Bellcore General Requirements GR-1000-CORE "General criteria for SONET dual feed unidirectional path switching ring (UPSR) equipment"
(January 1999), "SONET / SD" by M. Chow
Understanding H Standards and Applications "(pages 7-23 to 7-40 (1995)) and" SONET: A Guide to Synchronous Optical Networks "by W. Goralski.
(Pp. 342-366 (1997)). These are references of the present invention. In general, UPSRs become viable by using so-called working and protection paths with head-end bridging and tail-end switching at input and output nodes.

Using FIG. 1 as an example, the node 101-
104 are connected by the optical fiber 110 in the working path, and the optical fiber 1 in the protection path.
11 are connected. At node 102, tail-end switching is used to select signals from either the working path or the protection path to the output at node 102. Thus, the ring is U
In the case of certain failure situations within the PSR 100, it can survive because communication between nodes can be maintained.

In the case of a WDM-based UPSR, a multi-wavelength optical signal comprising a plurality of optical channels, each functioning at a different wavelength, is transmitted to optical fibers 110 and 1.
11 is transmitted by each. WDM-based UPS
In order to take advantage of optical transmission in R, it is desirable to remove and add individual optical channels from signals having multiple wavelengths at selected nodes in the ring.
For example, it may be desirable to add traffic over a particular optical channel at node 101 and delete traffic at node 102. Therefore, for the purpose of facilitating the addition and deletion of information to and from the optical channel, both the nodes 101 and 102 must have an optical addition / deletion function. Optical add / drop multiplexers are typically used for this purpose.

At each node, for example, SONET, in order to perform appropriate routing of traffic.
Note that optical and electronic additional equipment such as add / drop multiplexers, cross-connects, ATM switches, IP routers, etc. are required. For the purposes of understanding the principles of the present invention, the details of other electronic and optical devices used in processing added / removed traffic are not important.

In a WDM-based UPSR as shown in FIG. 1, wavelength assignment becomes a problem. Because
This is because communication is unidirectional and signals are bridged to both working and protection paths between nodes. For example, a signal from the node 101 to the node 102 on the optical fiber 110 and a signal from the node 102 to the node 101 propagate in the same direction. Similarly, optical fiber 1
Signals between nodes on 11 also propagate in the same direction. In such a case, the same wavelength is transmitted from node 101 to node 1.
When used for both communication to 02 and communication from node 102 to node 101, the wavelength will be occupied throughout the ring in optical fibers 110 and 111, both in the working and protection paths. . Thus, the possibility of wavelength reuse is eliminated because of the one-to-one correspondence between each connection and an individual optical channel having a particular wavelength, ie the assigned channel. More specifically, a separate optical channel (eg, having wavelength λ ₁ ) is used for communication between nodes 101 and 102, and another optical channel (eg, having wavelength λ ₂ ) is And so on used for communication between the node 103 and the like. Therefore, wavelength assignment in a WDM-based ring is an important consideration, especially from the viewpoint of the addition / deletion function of the WDM-based ring.

As mentioned above, the prior art approach to the wavelength add / drop multiplexer is to extract the entire signal strength of the selected wavelength at the add / drop node. Thus, existing add / drop arrangements typically include a wavelength selection component for adding / dropping individual optical channels from a composite multi-wavelength optical signal, ie, a WDM signal. However, these add / drop components have drawbacks as described below. 2 and 3 show two examples of wavelength addition / deletion elements for implementing a flexible addition / deletion function in a WDM application.

The addition / deletion arrangement shown in FIG.
An optical demultiplexer 201 is included that demultiplexes the composite WDM signal into individual optical channels that are constituent elements. In this example, each optical channel is an optical switch 2
02 and the wavelength addition / deletion element 205.
The wavelength adding / removing element is, for example, a Mach-Zehnder filter used for removing / adding individual optical channels associated with the same wavelength. Optical exchanger 2
02 is shown as a 1.times.2 switch used in the first position for normal through routing of the optical channel and in the second position used to add and / or delete the optical channel. The optical multiplexer 206 is then utilized for the purpose of recombining the individual constituent wavelengths into a composite WDM signal. The optical amplifier 210
They are usually placed to compensate for the losses that occur in the add / drop arrangement.

Among other problems, the cost due to the high insertion loss of such types of add / drop arrangements and the number of components required for WDM applications, especially in systems with a large number of channels. High, is the problem. For example, the multiplexer 20
6 can be as much as 20-24 dB. Another significant disadvantage is the bandwidth reduction effect due to cascading filters. Although not shown,
It should also be noted that separate transmitters and receivers are required for each channel added and removed. Eliminating optical switch 202 reduces costs and losses, but creates problems associated with in-service upgrades and the like. In particular, the use of a 1 × 2 switch allows for a relatively less disruptive (ie, non-disruptive) upgrade to the system. For example, a switch is installed from the beginning, and a wavelength adding / removing device can be added as required by a user.

FIG. 3 shows another example of a light addition / removal arrangement using a Bragg fiber grating as a wavelength selection element. This arrangement is known, for example, Gile
"Low Loss Add / Remove Multiplexers in WDM Lightwave Networks" by Tenth International Conf.
erence on Integrated Optics and Optical Fiber Comm
unication, Hong Kong, Vol. 3, pp. 66-67 (June 1995)). In this arrangement, optical circulator 215 has gratings 21 to remove and add optical channels via optical demultiplexer 217 and optical multiplexer 218, respectively.
6 is used. In operation, the grating 216 transmits the optical channel to be passed,
Optical channels to be deleted and added are reflective. As in previous arrangements, this approach suffers from cost and (to a lesser extent) losses due to the number and complexity of components. In addition, bandwidth reduction is still an issue as signals pass through successive gratings, and existing services are disrupted when upgrading services.

In accordance with the principles of the present invention, the use of broadband coupler-based add / drop elements with appropriate wavelength assignment and signal routing in a ring network has enabled the development of techniques for adding and removing optical channels comprising WDM signals. Is done. 4 and 5 show examples of a wideband coupler arrangement used in accordance with the principles of the present invention. FIG. 4 is useful in the case of single wavelength addition / deletion, and FIG. 5 is expanded in the case of multiple wavelength addition / deletion using appropriate multiplexing / demultiplexing elements.

More specifically, FIG. 4 is a diagram schematically showing a basic configuration block of an addition / deletion arrangement according to the principle of the present invention. Briefly, a broadband coupler or tap 300 (hereinafter referred to as coupler 300) allows an optical signal to be extracted from and / or added to a transmission mechanism, such as an optical fiber. To The coupler 300 has an input 301 for receiving a multi-wavelength WDM optical signal, and an input 302 for receiving an optical channel of a specific wavelength added to the WDM optical signal. Since the coupler 300 is broadband, each output 304 and 305 is a composite WD
Propagate M optical signals, that is, all wavelengths. However, the optical channel to be removed from the composite WDM optical signal is extracted from the WDM optical signal provided via output 304, while the WDM signal including the added optical channel is provided via output 305. .

[0024] Broadband couplers and taps and their operation are well known to those skilled in the art. As such, those skilled in the art can use various broadband optical couplers to implement the principles of the present invention. Generally, a coupler 300
Is contemplated to be any type of suitable optical device that distributes, splits, or combines light intensity between two or more ports. For the present invention, coupler 300 is referred to as being broadband. The reason is that the coupler 300 1) receives a WDM signal having a plurality of optical channels having different wavelengths; 2) extracts a certain portion of the optical signal strength of the WDM signal (tap-off) and taps off the WDM signal. And 3) providing the remaining portion of the light intensity of the WDM signal as an output to the optical transmission mechanism; and It is intended to have.

In the embodiment described herein, a "20/80" broadband coupler is contemplated for implementing the principles of the present invention. One example of this type of coupler is E-Tek Dynamics Inc.
A dual window broadband coupler manufactured by the company. This coupler has inputs 301 and 302
Approximately 20% of the optical signal strength provided via the tap output 304 is extracted, while approximately 80% of the optical signal strength is output via the output 305 as an output WDM signal. Note that this example is for illustrative purposes only, and that other coupling / tapping ratios may be used in implementing the principles of the present invention. For example, it is known that the coupling ratio of coupler 300 can be varied according to design and performance parameters in order to achieve a desired ratio of light transmitted to tap output 304 and output 305. Specifically, the ratio of the optical signal strength that is tapped off from the optical fiber is a matter of design choice, which is based on various parameters such as, for example, optical transmitter strength, receiver sensitivity, and fiber loss. For the embodiment shown here, the desired range of the optical signal strength to be tapped off is approximately 0.5 dB to 3 dB, for example, 1 dB.
dB. Again, these values are for illustrative purposes only and depend on various factors known to those skilled in the art.

FIG. 5 illustrates how the coupler 300 may be coupled with other components, such as the optical multiplexer 310 and the optical demultiplexer 311, in order to add / remove a plurality of optical channels having different wavelengths to the WDM optical signal. Is used as an example. Coupler 3
The operation and features of 00 are similar to the coupler already shown with respect to FIG. 4 and will not be repeated here for brevity.

In the UPSR 100 shown in FIG. 1, it is contemplated that one or more nodes 101-104 include an add / drop arrangement using a coupler 300 (FIGS. 4 and 5) in accordance with the present invention. Have been. More specifically, FIG. 6 illustrates an example of an add / drop arrangement in accordance with the principles of the present invention using couplers 300A and 300B that may be used in UPSR 100. As shown, the add / delete arrangement is the UPS of FIG.
Optical fiber 11 as working path in R100
0 is connected to the coupler 300A. Similarly, the coupler 300B is connected to the optical fiber 111 which is a protection path of the UPSR 100. Both couplers 300A and 300B provide λ ₁ , λ ₂ ,. . . , Λ _n , and receives a WDM signal comprising a plurality of optical channels having different wavelengths. As mentioned earlier,
The same signal is head-end bridged to both the working path and the protection path of the UPSR.

Couplers 300A and 300B are further connected at inputs 302A and 302B, respectively, to optical transmitters 315A and 315B, each of which transmits at a particular wavelength λ _{n + 1} to be added to the WDM signal. Supply the optical channel. It is contemplated that the optical transmitters 315A and 315B have fixed wavelengths or are tunable, wavelength selective, directly or externally modulated, and the like. Examples of different devices used to supply optical carriers (ie, optical channels having a particular wavelength) and to modulate data onto the optical carrier are known to those skilled in the art. Thus, for the sake of simplicity of explanation and illustration, the components required to add traffic (ie, data) to a WDM signal are collectively represented in an optical transmitter. In accordance with another aspect of the present invention, which will be described in detail below in the context of a particular network deployment, the optical transmitters 315A and 315B may be separate devices as shown in FIG. It can be implemented as a transmitter. In the latter case, the optical transmitter is connected to a distribution device (not shown) such as, for example, a 1 × 2 power splitter, and the coupler 3
Provide an optical channel (having the same wavelength) to each of 00A and 300B.

The couplers 300A and 300B are further connected to optical filters 316A and 316B at outputs 304A and 304B, respectively. As described above, couplers 300A and 300B are broadband couplers and combine WDM optical signals (ie, λ ₁ ,
λ ₂ ,. . . , Λ _n ) are tapped off at the coupler. Therefore, the optical filter 31
6A and 316B are needed to filter out optical channels having a particular wavelength λ _drop to be removed from the WDM optical signal. Here, λ _drop represents one or more of the constituent optical channels (ie, λ ₁ , λ ₂ ,..., Λ _n ). Optical filters,
Other components for separating or splitting a composite WDM optical signal into constituent optical channels are known to those skilled in the art.

The optical channels filtered from each of the working path and the protection path, ie, the component channels to be removed from the WDM optical signal, are supplied to the optical protection switching element 318. In this embodiment, switching element 318 implements a tail-end switching function in UPSR 100 that selects the signal provided by either the working path or the protection path according to the particular protection switching arrangement used. Thereafter, the selected optical channel is provided to an appropriate optical receiver 320 for appropriate processing at the deleted node. Modulated optical carrier (ie, optical channel with a specific wavelength)
Specific examples of the different devices used to receive and process the data are known to those skilled in the art. Thus, for the sake of simplicity of explanation and illustration, the components required to remove traffic (eg, data) from a WDM signal are collectively represented by an optical receiver.

Furthermore, because the couplers 300A and 300B are broadband, a portion of the composite WDM optical signal (λ ₁ , λ ₂ ,..., Λ _n ) including the added optical channel (λ _{n + 1} ) , Optical fibers 110 and 1 on the working path and the protection path via outputs 305A and 305B, respectively.
11 is supplied. Thus, the broadband coupler 3
00A and 300B implement deletion and continue operation.

It should be noted that the above-described embodiment can be modified to implement an electronic protection exchange. For example, an optoelectronic receiver may be used instead of the optical filters 316A and 316B, and then the switch 3
An electronic switch, i.e., a 2x1 switch, that implements 18 tail-end switching functions may be deployed.

The use of wideband couplers for adding and removing signals can cause crosstalk problems. Specifically, since the signal is incident (i.e., added) and extracted (i.e., removed) through the same tap or coupler, the incident signal may "leak" into the extracted signal. . This undesirable effect can be exacerbated by the fact that the incident signal typically has a higher optical signal strength than the extracted signal. For example,
This potential leakage is the result of channel separation and crosstalk characteristics of certain optical filters and demultiplexers used to filter out optical channels having certain wavelengths to be removed from the WDM signal. Thus, FIG. 7 illustrates an embodiment in accordance with the principles of the present invention for substantially reducing or eliminating this undesirable effect using adaptive equalization or cancellation.

More specifically, FIG. 7 shows a coupler 300 having characteristics similar to those already described in the previous embodiment. For the sake of brevity, only the differences between this embodiment and the previous embodiment are described below. As shown, coupler 300
Is connected to the optical demultiplexer 325 via the output 304. The demultiplexer 325 is connected to the coupler 30
Receiving a portion of the composite WDM signal tapped off by 0 and separating the composite WDM signal into individual optical channels having different wavelengths. Because of the aforementioned crosstalk and channel separation limits in such devices, such as optical demultiplexers, the tapped-off WDM optical signal is an unwanted signal from optical channel λ _{n + 1} added at the input of coupler 300. May have components.
Therefore, the individual optical channel λ _drop to be dropped at this node may also include this unnecessary signal component.

To alleviate this problem, the individual optical channel (λ _drop ) to be removed at this node is directed to a device such as optical detector 326 and converted to an electrical signal. The operation of light detectors and equivalent devices is well known to those skilled in the art. Thereafter, the electrical signal is directed to an amplifier 327 according to conventional techniques. The amplified electric signal is supplied to a subtraction circuit 328, and the signal is supplied to the node (the coupler 300).
The added signal is subtracted from the signal removed at that node). Other techniques for removing unwanted signal components from a tapped-off signal are known to those skilled in the art and are included in the present invention.

For a better understanding of the principles of the present invention,
Some example ring network arrangements using the broadband coupler-based add / drop arrangements according to the present invention described in the above embodiments are described below.

EXAMPLE 1 (Unidirectional Route Switching Ring) FIGS. 8 to 11 are diagrams schematically showing a unidirectional route switching ring (UPSR) 400 using the principle of the present invention. UPSR 400 has nodes 401-403 and a node 405 with a special function called a terminating node for reasons described in more detail below. The nodes 401 to 403 and the terminal node 405 are hereinafter referred to as a working path 410 and a protection path 411, respectively.
Are interconnected in a ring arrangement via optical fibers 410 and 411 called. The basic principles of UPSR are well known and are briefly summarized in the description according to FIG. Nodes 401-403 may include the broadband coupler-based add / drop arrangement described in the embodiments described above (eg, FIGS. 4-6). However, in the embodiment shown in connection with FIGS. 8-11, communication between nodes 402 and 403 is illustrated. Therefore, at least the nodes 402 and 40
It is assumed that each of the three includes the broadband coupler-based add / drop arrangement shown in FIG.

Furthermore, in this embodiment, a termination node 405 is required due to the optical self-interference problem that can occur in a closed ring architecture. As is well known, such problems can occur when an optical channel having a particular wavelength used to carry traffic between two nodes continues to propagate in the ring forever. Generally, circulation (recirculation) is not allowed in order to avoid the self-interference problem. In accordance with the principles of the present invention, self-interference effects are substantially reduced by converting an input optical signal to an electrical signal at a termination node and then back to an optical signal. Specifically, the terminating node 405 is used in the ring for the purpose of serving as the originating and terminating point of the ring. At the termination node 405, a certain signal is added, a certain signal is deleted, a certain signal passes (normal passage), and a certain signal is terminated or suppressed. For example, the function of the terminating node may be performed at a central node (eg, a central office location) or at a common cross-connect node serving as an interface to multiple rings. Note that the terminating node 405 can also be used for network monitoring purposes and for sending control and management information to other nodes in the ring.

FIG. 16 is a block diagram briefly showing an embodiment of a terminal node according to the present invention. In short,
The terminal node has a component for demultiplexing and multiplexing a WDM optical signal, a component for converting the wavelength of each optical channel, and a component for adding / deleting a signal. FIG.
The terminal node 405 shown in FIG.
The terminal node is connected to the working path 410 and the protection path 411. At the termination node 405, an optical demultiplexer 4200 is connected to the working path 410 to separate WDM optical signals into individual optical channels. Some of the optical channels are connected to a wavelength converter 421. For example, an optical conversion unit (OT
Wavelength converters such as U) are known to those skilled in the art. OTU
Using as an example, an optical signal is first converted to an electrical signal and then reconverted to an optical signal having a different wavelength. The need for a wavelength converter will be described in more detail below in connection with the operation of the UPSR shown in FIGS. Some of the demultiplexed optical channels are terminated or suppressed at termination element 450. Various optical signal termination methods and devices, such as optical detectors and receivers, are known to those skilled in the art.

After appropriate wavelength conversion or termination, the individual optical channels are combined by an optical multiplexer 422 into a composite WD.
It is multiplexed with M optical signals. While complete demultiplexing and subsequent multiplexing of all channels at the terminating node 405 is contemplated, there are multiple methods and wavelength plans implemented to achieve this function. One example is the so-called Dragonone router.
And waveguide array router multiplexer / demultiplexer. See U.S. Pat. No. 5,002,350. This US patent is a reference to the present invention. However, other solutions will be apparent to those skilled in the art and are contemplated in the present invention.

Connected to the protection path 411 are an optical demultiplexer 420, a multiplexer 422, a wavelength converter 421, and a termination element 450, all of which correspond to the corresponding components already described in relation to the working path 410. Are the same. As shown, the wavelength add / drop elements 490 add / drop optical channels appropriately.
Working path 410 and protection path 4
11 are connected to each other. For simplicity of illustration, the wavelength add / drop element 490 is shown as a single functional block, but the wavelength add / drop element 490 uses the broadband coupler-based add / drop arrangement shown in FIG. It is clear that it is possible to implement even if.

As shown in FIGS. 8 to 11, U
Signals can be added and deleted in the PSR 400. Composite W composed of optical channels having different wavelengths
Although the DM signal propagates through the UPSR 400, for the sake of simplicity, only the optical channels that are actually added and removed at the selected node are shown in the ring with dashed arrows. 8 and 9 show communication from the node B (402) to the node C (403). Node B
In the clockwise direction on working path 410 (FIG. 8), and in the counterclockwise direction on the protection route 411 (FIG. 9), respectively and sends the data by the optical channel lambda _1. In FIG.
Working path 41 may be implemented using a broadband coupler-based add / drop arrangement as shown in FIG.
A portion of the optical signal strength of the WDM optical signal from 0 is tapped off, and the traffic carried by optical channel λ ₁ is removed at node C. The remainder of the optical signal strength in the optical channel λ ₁ of the WDM signal on the working path 410 is terminated by the termination element 450 at the termination node 405. Destination node (node C)
One reason for terminating or suppressing optical channel λ ₁ after passing through is to prevent interference that can occur due to the optical channel circulating and arriving at the original Node B added to the ring. It is.

As shown in FIG. 9, the WDM signal (including the optical channel λ ₁ ) propagates on the protection path 411 in the counterclockwise direction. When received at terminal node 405, the wavelength of optical channel λ ₁ is converted to optical channel λ ₃ . One reason to convert the wavelength of an optical channel that has not passed through the destination node is that the optical channel having the original wavelength, e.g., optical channel λ ₁ , will be up to the original Node B where it was added to the ring. This is to avoid interference that may occur due to circulation. As shown, node C taps off a portion of the optical signal strength of the WDM optical signal from protection path 411, and the traffic carried on optical channel λ ₃ is removed at node C. The remainder of the optical signal strength in the optical channel λ ₃ of the WDM signal on the protection path 411 is terminated by the termination element 450 at the termination node 405.

The wavelength allocation and use of the termination node 405 in the UPSR 400 shown in FIGS. 8 and 9 illustrate an important aspect of wavelength reuse. In particular, the broadband coupler is a WDM at a particular node.
Rather than extracting a specific wavelength of the optical signal, it only taps off a portion (ie, all wavelengths) of the optical signal strength of the WDM optical signal, so the WDM optical signal (ie, all wavelengths)
Still propagates the ring. Thus, individual wavelengths of optical channels added and deleted between nodes on the ring cannot be reused. For example, from node 402 to node 4
The optical channel carrying traffic to 03 (added at node B and removed at node C) carries traffic from node 403 to node 402 (added at node C and removed at node B). It cannot be used for optical channels. Therefore, additional / in accordance with the principles of the present invention
The truncation arrangement requires different wavelengths to support each connection in the ring. For example, λ ₁ from B to C, λ ₂ from C to B, and so on.

Similarly, FIG. 10 and FIG.
2 to a node B. Node C is
Channel λ_TwoClockwise on working path 410
To the protection path 411 in the counterclockwise direction.
Put out. As shown in FIG.
5 is the optical channel λ_TwoWavelengths as described above
From the optical channel λ_ThreeConvert to As shown
Node B receives the WDM optical signal from the working path 410
Tap off a portion of the optical signal strength of _Threeso
The carried traffic is deleted at Node B. Work
Channel λ of the WDM optical signal in the switching path 410_Three
The remaining optical signal strength at
And is terminated by the termination element 450. As shown in FIG.
As shown in FIG.
Tap off some of the optical signal strength of the signal and
Flannel λ_TwoTraffic carried by is removed at Node B
You. Optical channel of WDM optical signal in protection path 411
λ_TwoThe remaining optical signal strength at
At the termination element 450.

In the embodiment shown in FIGS. 8-11, a given node adds an optical channel having the same wavelength to both the working path and the protection path,
An optical channel having a different wavelength from the working path and the protection path is received and deleted. In another embodiment, it may be desirable for a node to add optical channels having different wavelengths to the working and protection paths while receiving and removing optical channels having the same wavelength. This latter embodiment is shown in FIGS. Since the same principles of operation as described in connection with FIGS. 8-11 apply equally to the embodiments shown in FIGS. 12-15, the same is true for the sake of brevity. It is not described repeatedly. Other modifications that fall within the scope of the invention will be apparent to those skilled in the art and are intended to be of the invention.

Example 2 (Unidirectional Line Switched Ring) An add / drop arrangement in accordance with the principles of the present invention is advantageously used in a second type of ring network, the so-called Unidirectional Line Switched Ring (ULSR) network. Can be The basic operating principles of ULSR networks are also known. Briefly, nodes in the ULSR communicate by routing signals in the same direction, ie, unidirectional, only on the working path. In case of node failure, cable disconnection or other failure,
The node adjacent to the failed location implements a so-called "loopback exchange" and the signal is routed through the protection path in the opposite direction to the working path.

In accordance with the principles of the present invention, the WDM signal is ULSR using a wideband coupler-based add / drop arrangement.
Are added and deleted. 17 and 18 show a unidirectional line exchange ring (U) using the principles of the present invention.
LSR) 500 is shown. As shown,
ULSR 500 includes nodes 501-503 and terminal node 505. Nodes 501-503 and termination node 505 are interconnected in a ring arrangement via working path 510 and protection path 511 and optical fibers 510 and 511 that fail. UP mentioned above
As with the SR example, nodes 501-503 may each include a broadband coupler-based add / drop arrangement. However, in the embodiment shown in FIGS. 17 and 18,
Nodes 502 and 5 when a failure occurs between nodes 501 and 502 (that is, nodes A and B)
03 (ie, node B and node C) are illustrated. Thus, it is assumed that at least nodes 502 and 503 each include a broadband coupler-based add / drop arrangement.

Although a composite WDM signal consisting of a plurality of optical channels having different wavelengths propagates through the ring, for the sake of simplicity, only the optical channels that are actually added and deleted at the selected node are shown. This is indicated by the dotted arrow in the ring. In FIG. 17, node B sends data in a clockwise direction to node C via optical channel λ ₁ on working path 510. Node C
Working path 510 to W using a broadband coupler-based add / drop arrangement (not shown) in accordance with the principles of the present invention.
A portion of the optical signal strength of the DM optical signal is tapped off, and the traffic carried by λ ₁ is removed at node C.
The remaining optical signal strength on the optical channel λ ₁ of the WDM optical signal in the working path 510 is
At 5 is terminated by a terminating element 550.

As shown in FIG.
Sends data in the clockwise direction to the Node B via the optical channel λ ₃ on the working path 510. For the same reason as those described in the foregoing are the embodiments, termination node 505 converts the wavelength of optical channel lambda ₃ to the optical channel lambda _2. Because of the failure situation 560 between node A and node B, node A and node B implement loopback switching according to known techniques for line switching rings. Therefore, the WDM optical signal is received at the working path 510 at the node A, is looped back on the protection path 511, and propagates to its destination, that is, the node. At its destination, Node B, the WDM signal is looped back to working path 510 again. The Node B taps off a portion of the optical signal strength of the WDM optical signal from the working path 510 using a broadband coupler-based add / drop arrangement (not shown) in accordance with the principles of the present invention to provide an optical channel λ. _Two
The traffic carried by is deleted at the Node B. WD
The residual optical signal strength of the M optical signal in the optical channel λ ₂ is
The signal propagates through the working path 510 to reach the termination node 505 and is terminated by the termination element 550.

Note that in many cases, if the terminal node fails, traffic in the network may not be able to survive. For example, if a terminal node fails and an adjacent node implements loopback switching, the signal does not propagate through the terminal node 505, and appropriate wavelength conversion and suppression / termination are not performed. As a result, the interference problem described above occurs.

FIG. 19 is a diagram schematically showing one embodiment of a wideband coupler-based addition / deletion arrangement which can be used for adding / deleting signals in ULSR 500 (FIGS. 17 and 18). It will be apparent to those skilled in the art that the arrangement shown in FIG. 19 is a modification of the embodiment shown in FIG. 6 in connection with the UPSR. Thus, for the sake of brevity, common elements and functions are not repeated here. Instead, only significant differences are described, most of which are the working paths 51 of the add / delete arrangement.
0 and protection paths 511 and the exchange and routing of signals from these paths via the broadband coupler 601.

As shown, the addition / deletion arrangement 6
00 is a broadband coupler 601, an optical transmitter 60
2, an optical filter 603, and an optical receiver 604, each of which operates in a manner similar to that described with respect to the arrangement shown in FIG. However, add /
The elimination arrangement 600 further comprises at least two light exchangers 610 and 611, which are now 2 ×
Shown as a two light exchanger. Optical exchangers 610 and 6
11 can be implemented, for example, with a photoelectric exchanger, a mechanical optical exchanger, a lithium niobate exchanger, a polymer-based exchanger, and the like. Other devices suitable for routing optical signals in accordance with the principles of the present invention will be apparent to those skilled in the art.

In normal operation, ie, when not in a fault situation, switches 610 and 611 are in a crossbar condition. More specifically, a signal input to the switch 611 via the working path 510 is switched or routed to the optical coupler 601. In coupler 601 the addition and deletion of optical channels is performed as described above in connection with the embodiment shown in FIG. The WDM optical signal output from coupler 601 propagates to switch 610 and is switched or routed to working path 510.

A fault exists in the ring (for example, FIG.
18 and failure 560 in ULSR 500 of FIG. 18), the node adjacent to the failure (ie, node A or B) implements a loopback exchange and routes the signal accordingly. In some cases, the exchanger 611 (exchanger B) changes to a so-called bar state,
11 (exchanger A) remains in the crossbar state. In such a situation, the signal input to switch 611 (switch B) via working path 510 is directly looped back to protection path 511 by switch 611. Signals received from protection path 511 by switch 610 (switch A) are switched via path 615. This is because the exchanger 610 (exchanger A) is in a crossbar state. Since switch 611 (switch B) is in the bar state, the signal from protection path 511 is routed through coupler 601 and the appropriate add / drop operations are performed as described above. The signal output from coupler 601 is routed to working path 510 via switch 610 (switch A) which is still in a crossbar state. Note that the change in each state of the optical switch in this embodiment, ie, the crossbar or bar state, depends on the location of the fault for that node.

Example 3 (Two-Fiber Bidirectional Line Exchange Ring) An add / drop arrangement in accordance with the principles of the present invention is another type of ring network, a so-called bidirectional line exchange ring (B
It can also be used advantageously in LSR) networks.
As in the case of UPSR and ULSR networks, BL
SR networks are known in the SONET / SDH domain. For example, Bellcore General Request GR-123
0-CORE, "General Standards for SONET Bidirectional Line Exchange Ring Devices" (December 1999), "Understanding SONET / SDH Standards and Applications" by M. Chow (pages 7-23 to 7-40 ( 1995
)) And “SONET: A Guide to Synchronous Optical Networks” by W. Goralski (pages 342 to 366 (1)).
997)). These are references of the present invention.

According to the principles of the present invention, the WDM signal is
Using a broadband coupler-based add / drop arrangement located at one of a plurality of nodes in an LSR, the BLSR
Added and deleted within More specifically, FIG.
FIG. 2 is a diagram showing an example of a two-fiber bidirectional line exchange ring (2F-BLSR) using the principle of the present invention. 2
The F-BLSR 650 has the same basic physical configuration as the network described above. To elaborate,
Nodes 651-653 and termination node 655 are interconnected via optical fibers 660 and 661 in a ring arrangement. However, the difference from a 2F-BLSR network when compared to a unidirectional ring occurs in its traffic flow. For example, in a 2F-BLSR network, each optical fiber 660 and 66
The band at 1 is split such that half is for working traffic and the other half is for protection traffic. Further, traffic flows clockwise in the optical fiber 660, and traffic flows counterclockwise in the optical fiber 661.

The composite WDM signal propagates throughout the ring
Has been selected at the selected node for simplicity of illustration.
Only optical channels actually added and deleted are in the ring
Are indicated by dotted arrows. FIG. 20 (normal operation)
In other words, the node 652 (node B)
Optical channel λ using a working band of 0₁Through
Send data to node 653 (node C) in the clockwise direction
Put out. Similarly, the node 653 (node C)
Optical channel λ using the working band of bus 661 _TwoThrough
And sends data in the counterclockwise direction. The fruit mentioned above
Addition / deletion arrangement of broadband coupler base as in the example
(Not shown) is the optical channel λ₁And λ_TwoAddition and deletion
For both nodes 652 and 653
It has been. The optical signals λ1 and λ2 are as described above.
At the termination node 655 for the same reasons as
Is terminated.

FIG. 21 and FIG. 22 show the node B and the node C, respectively.
21 shows the operation of the 2F-BLSR in the case where the communication with has failed, FIG. 21 shows the communication from the node B to the node C, and FIG. 22 shows the communication from the node C to the node B. In general, loopback switching is used in a manner similar to that described above for the ULSR example, except that the traffic flow between the working band and the guard band on each of the optical fibers 660 and 661 is different. Specifically, in response to failure 670, both Node B and Node C implement a loopback exchange.

In FIG. 21, Node B in the loopback switching mode is a WDM (including optical channel λ ₁ )
The optical signal is routed from the working band of optical fiber 660 to the guard band of optical fiber 661. Optical channel λ ₁ is not terminated at termination node 655. This is because the destination has not yet been reached. The node C loop-back exchanges the WDM optical signal from the protection band of the optical fiber 661 to the working band of the optical fiber 660 again. By using a broadband coupler-based arrangement according to the principles of the present invention, the traffic carried by optical channel λ ₁ is eliminated at node C. The optical signal strength remaining in the optical channel λ ₁ of the WDM optical signal in the working band of the optical fiber 660 is terminated at the termination node 655 in the same manner as described above.

In FIG. 22, optical channel λ ₂ is routed from node C to node B along 2F-BLSR in a manner similar to that described above. The clear difference is that the WDM optical signal (including optical channel λ ₂ ) is looped back at node C from the working band of optical fiber 661 (counterclockwise) to the guard band of optical fiber 660 (clockwise). Exchanged and the opposite is done at Node B.

Another distinct difference in 2F-BLSR 650 is that the termination node 655 passes or passes through an optical channel having a particular wavelength in both optical fiber 660 (clockwise) and optical fiber 661 (counterclockwise). It must be possible to terminate. However, wavelength conversion is not required, and thus fewer wavelengths are used to implement signal addition / deletion between nodes in the ring. For example, no wavelength conversion is required if no fault has occurred and all connections between any two node sets are routed without passing through the termination node 655. In this case, the termination nodes are optical fibers 660 and 66
1 to terminate or suppress all wavelengths from both. If a failure occurs in the ring and loopback exchange is started to isolate the failure, the end node passes only those wavelengths that have not reached the destination node.

FIG. 23 is a diagram showing the structure of FIG.
Broadband coupler-based add / drop arrangement 700 used at nodes 651-653 of F-BLSR 650
FIG. 3 is a diagram showing one embodiment of the present invention. Addition shown in FIG.
The structure and operation of the delete arrangement 700 is similar to that described above with respect to FIG. 19, except that additional broadband couplers and corresponding components for adding and deleting individual optical channels are used. is there. More specifically, the add / drop arrangement 700 includes a pair of broadband couplers 701A-701B and a pair of optical transmitters 70.
2A-702B, a pair of optical filters 703A-703
B, a pair of optical receivers 704A-704B, and a pair of optical exchangers 710 and 711 for connecting to the optical fibers 660 and 661. The added coupler 701B and its associated transmitter 702B, filter 703B, and receiver 704B are used, for example, to add and remove signals to and from the working bands of both optical fibers 660 and 661. As in the previous embodiment, switches 710-711 operate in a crossbar state during normal operation (i.e., no fault). Similarly, the optical switches 710-711
Changes to a state that implements a loopback function, that is, a bar state and a crossbar state, depending on the location of the fault with respect to the node.

Example 4 (Four-Fiber Bidirectional Line-Switching Ring) Another known optical ring network architecture is the so-called four-fiber bidirectional line-switching ring (4F-BLS).
R), the structure and operation of which are known to those skilled in the art. Briefly, 4F-BLSR is based on the fact that individual optical fibers are used for each flow traffic of working traffic in a clockwise direction / working traffic in a counterclockwise direction / protective traffic in a clockwise direction / protective traffic in a counterclockwise direction. Except for exclusive use, it performs the same operation as 2F-BLSR.

FIGS. 24 and 25 show a four-fiber bidirectional line exchange ring (4F-BLSR) 80 during normal operation.
0 and FIGS. 26 and 27 show the 4F-BLSR 800 in the case where there is a failure in the ring. As shown, nodes 801-804 include:
Optical fiber 810 (clockwise working path),
Optical fiber 811 (working path in the counterclockwise direction), optical fiber 820 (protection path in the clockwise direction),
And an optical fiber 821 (protection path in the counterclockwise direction) and interconnected in a ring arrangement. For reasons that will be described in detail below, the optical fibers 810 and 811 that are the working paths in the clockwise and counterclockwise directions, respectively, do not constitute a closed ring. However, the optical fibers 820 and 821, which are the protection paths in the clockwise direction and the counterclockwise direction, respectively, constitute closed rings.

In FIG. 24, the node 802 (node B) sends data to the node 803 (node C) on the optical channel λ ₁ using the clockwise working fiber 810. In FIG. 25, the node C sends data to the node B on the optical channel λ ₁ using the working fiber 811 in the counterclockwise direction. The composite WDM signal propagates along the ring,
For simplicity of illustration, only the optical channels that are actually added and removed at the selected node are indicated by the dotted arrows in the ring. The WDM signal may be transmitted (eg, on the optical channel λ ₁ between node and node C) using a broadband coupler-based add / drop arrangement (not shown) as described in connection with the previously described embodiments. like)
It is added and deleted in 4F-BLSR800.

A significant difference in operation from other embodiments relates to wavelength termination and conversion. Specifically, since the working fiber 810 in the clockwise direction and the working fiber 811 in the counterclockwise direction do not form a closed ring, no special termination is required in the 4F-BLSR 800. Furthermore, interference is avoided by simply not connecting the working fiber between the node pairs on the ring. For example, the optical channel λ propagating along the ring after being tapped off at the corresponding node (ie, node C for working fiber 810 in the clockwise direction and node B for working fiber 811 in the counterclockwise direction). The residual optical signal strength at ₁ is simply terminated at each end, as shown. This example is for illustrative purposes. Thus, other means for terminating or suppressing an optical channel having a particular wavelength at the end of the working fiber will be apparent to those skilled in the art. Also, no wavelength conversion is required, and only a single wavelength is required for full duplex connection between any two nodes in the 4F-BLSR 800.

FIG. 26 and FIG.
4F-BLSR8 when a fault 825 exists between
FIG. 26 shows the communication from node B to node C, and FIG. 27 shows the communication from node C to node B. In general, loopback exchange is used as in the previous embodiment, but there are differences as described below. In this particular embodiment, both Node B and Node C have failed 825
To implement loopback exchange.

In FIG. 26, the Node B in the loopback switching mode is a WDM (including optical channel λ ₁ )
The optical signal is routed from the clockwise working fiber 810 to the counterclockwise protection fiber 821. WDM optical signals (including optical channel λ ₁ ) propagate in the ring as shown. At the node C, the WDM optical signal is looped back from the protection fiber 821 in the counterclockwise direction to the working fiber 810 in the clockwise direction. By using a broadband coupler-based arrangement (not shown) in accordance with the principles of the present invention, traffic carried on optical channel λ ₁ is dropped at node C. The residual optical signal strength of the optical channel λ ₁ in the WDM optical signal in the clockwise working fiber 810 is terminated as described above.

Similarly, as shown in FIG. 27, the node C in the loopback switching mode transmits the WDM optical signal (including the optical channel λ ₁ ) clockwise from the working fiber 811 in the counterclockwise direction. Protection fiber 8 in direction
Route to 20. (Including optical channel λ ₁₎ W
The DM optical signal propagates in the ring as shown. At the node B, the WDM optical signal is looped back from the protection fiber 820 in the clockwise direction to the working fiber 811 in the counterclockwise direction. By using a broadband coupler-based arrangement (not shown) in accordance with the principles of the present invention, traffic carried on optical channel λ ₁ is dropped at Node B. The residual optical signal strength of the optical channel λ ₁ in the WDM optical signal in the working fiber 811 in the counterclockwise direction is terminated as described above. The well-known technique of span exchange is also 4F-BLSR
Can be used instead of the loopback exchange in.

FIG. 28 is a block diagram of the fourth embodiment shown in FIGS.
9 illustrates one embodiment of a broadband coupler-based add / drop arrangement 900 that may be used at nodes 801-804 in F-BLSR 800. The structure and operation of the addition / deletion arrangement 900 shown in FIG.
3 is the same as that described with respect to No. 3 except for the difference relating to the loopback exchange function described above. For example, to implement a loopback exchange between the clockwise working fiber 810 and the counterclockwise protection fiber 821, the add / drop arrangement 900 includes a pair of switches 9
10-911, a broadband coupler 901 and an associated transmitter 902, filter 903, and receiver 904. Similarly, the working fiber 811 in the counterclockwise direction and the protection fiber 82 in the clockwise direction
0 to implement a loopback exchange between
Deletion arrangement 900 includes a pair of switches 920-921, a broadband coupler 915, and an associated transmitter 91.
6, a filter 917, and a receiver 918.

As in the previous embodiment, the switch 910-
911 and 920-921 are in a crossbar state when the ring is in normal operation (i.e., there is no fault). Similarly, exchangers 910-911 and 920-92
1 changes its state to a state that implements loopback exchange, that is, a bar state or a crossbar state, depending on the relative position of the fault with respect to the node. The traffic flow in different directions and its operation in the add / drop arrangement 900 follow the same basic principles as described in the embodiments described above.

The above description relates to one embodiment of the present invention, and those skilled in the art can consider various modifications of the present invention, but all of them are within the technical scope of the present invention. Is included. For example, add / drop arrangements in accordance with the principles of the present invention may be used for optical ring architectures (eg, different ring topologies, different numbers of nodes, etc.) as not shown or described herein. Is also applicable. The principles of the present invention are equally applicable to networks with optical amplifiers and networks without optical amplifiers. further,
It will also be apparent to one of ordinary skill in the art that various combinations of the optical and electronic components shown in the exemplary structures for performing the add / drop and protection exchange functions described herein may be substituted.

[0074]

As described above, according to the present invention, W
Provided are a method, a system, and an apparatus for realizing addition and deletion of an optical signal in DM or DWDM at lower cost.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an example of a ring network.

FIG. 2 is a block diagram schematically illustrating a typical addition / deletion arrangement in a multi-wavelength optical system according to the related art.

FIG. 3 is a block diagram schematically illustrating a typical addition / deletion arrangement in a multi-wavelength optical system according to the related art.

FIG. 4 is a simplified block diagram illustrating a broadband coupler used in a wavelength add / drop element in accordance with the principles of the present invention.

FIG. 5 is a simplified block diagram illustrating a broadband coupler used in a wavelength add / drop element in accordance with the principles of the present invention.

FIG. 6 is a schematic diagram illustrating an example of an addition / deletion arrangement using the wideband coupler illustrated in FIG. 3 in a unidirectional path switching ring (UPSR) network.

FIG. 7 is a schematic diagram illustrating another embodiment of an add / drop arrangement in accordance with the principles of the present invention.

FIG. 8 is a simplified schematic diagram illustrating an example network illustrating the principles of the present invention used in communications in a UPSR network.

FIG. 9 is a simplified schematic diagram illustrating an example network illustrating the principles of the present invention used in communications in a UPSR network.

FIG. 10 is a simplified schematic diagram illustrating an example network illustrating the principles of the present invention used in communications in a UPSR network.

FIG. 11 is a schematic diagram illustrating a simplified network example illustrating the principles of the present invention used in communications in a UPSR network.

FIG. 12 is a simplified schematic diagram illustrating an example network illustrating the principles of the present invention used in communications in a UPSR network.

FIG. 13 is a simplified schematic diagram illustrating an example network illustrating the principles of the present invention used in communications in a UPSR network.

FIG. 14 is a simplified schematic diagram illustrating an example network illustrating the principles of the present invention used in communications in a UPSR network.

FIG. 15 is a simplified diagram illustrating a simplified network example illustrating the principles of the present invention used in communications in a UPSR network.

FIG. 16 is a simplified block diagram of a single node in the networks shown in FIGS. 8-15 in accordance with the principles of the present invention.

FIG. 17 is a simplified block diagram of an example network illustrating the principles of the present invention in communicating over a Unidirectional Line Switched Ring (ULSR) network.

FIG. 18 is a block diagram that briefly illustrates an example network that illustrates the principles of the present invention in communicating over a Unidirectional Line Switched Ring (ULSR) network.

FIG. 19 is a block diagram schematically illustrating an example of an addition / deletion arrangement using the wideband coupler illustrated in FIG. 3 in the ULSR network illustrated in FIGS. 17 and 18;

FIG. 20: Two-fiber bidirectional line exchange ring (2F
-A block diagram briefly illustrating an example network illustrating the principles of the present invention in communication over a (BLSR) network;

FIG. 21: Two-fiber bidirectional line exchange ring (2F
-A block diagram briefly illustrating an example network illustrating the principles of the present invention in communication over a (BLSR) network;

FIG. 22: Two-fiber bidirectional line exchange ring (2F
-A block diagram briefly illustrating an example network illustrating the principles of the present invention in communication over a (BLSR) network;

FIG. 23 shows 2F- shown in FIGS. 20 to 22;
FIG. 4 is a block diagram schematically illustrating an example of an addition / deletion arrangement using the broadband coupler illustrated in FIG. 3 in a BLSR network.

FIG. 24: 4-fiber bidirectional line exchange ring (4F
-A block diagram briefly illustrating an example network illustrating the principles of the present invention in communication over a (BLSR) network;

FIG. 25: 4-fiber bidirectional line exchange ring (4F
-A block diagram briefly illustrating an example network illustrating the principles of the present invention in communication over a (BLSR) network;

FIG. 26: 4-fiber bidirectional line exchange ring (4F
-A block diagram briefly illustrating an example network illustrating the principles of the present invention in communication over a (BLSR) network;

FIG. 27: 4-fiber bidirectional line exchange ring (4F
-A block diagram briefly illustrating an example network illustrating the principles of the present invention in communication over a (BLSR) network;

FIG. 28 is a view showing 4F- shown in FIGS.
FIG. 4 is a block diagram schematically illustrating an example of an addition / deletion arrangement using the broadband coupler illustrated in FIG. 3 in a BLSR network.

[Explanation of symbols]

REFERENCE SIGNS LIST 100 Unidirectional path switching ring (UPSR) 101, 102, 103, 104 Node 110, 111 Optical fiber 201 Optical demultiplexer 202 Optical switch 205 Wavelength adding / dropping element 206 Optical multiplexer 210 Optical amplifier 215 Optical circulator 216 Grating 217 Optical Demultiplexer 218 Optical multiplexer 300 Broadband optical coupler 301, 302 Input 304, 305 Output 310 Optical multiplexer 311 Optical demultiplexer 315 Optical transmitter 316 Optical filter 318 Optical switch 320 Optical receiver 325 Optical demultiplexer 326 Optical detector 327 Amplifier 328 Subtraction circuit 400 Unidirectional path switching ring (UPSR) 401, 402, 403 Node 405 Terminal node 410, 411 Optical fiber B 420 Optical demultiplexer 421 Wavelength converter 422 Optical multiplexer 450 Termination element 490 Wavelength addition / deletion element 500 Unidirectional line exchange ring (ULSR) 501, 502, 503 Node 505 Termination node 510, 511 Optical fiber 550 Termination element 600 Addition / Delete arrangement 601 Broadband optical coupler 602 Optical transmitter 603 Optical filter 604 Optical receiver 610, 611 Optical switch 615 Path 650 Two-fiber bidirectional line switching ring (2F-B
LSR) 651, 652, 653 Node 655 Termination node 660, 661 Optical fiber 700 Addition / deletion arrangement 701 Broadband optical coupler 702 Optical transmitter 703 Optical filter 704 Optical receiver 710, 711 Optical switch 800 4-fiber bidirectional line exchange ring (4F) -B
LSR) 801, 802, 803, 804 Node 810, 811, 820, 821 Optical fiber 900 Addition / deletion arrangement 901, 915 Broadband optical coupler 902, 916 Optical transmitter 903, 917 Optical filter 904, 918 Optical receiver 910, 911, 920 , 921 optical exchanger

 ──────────────────────────────────────────────────続 き Continuation of the front page (71) Applicant 596077259 600 Mountain Avenue, Murray Hill, New Jersey 07974-0636 U.S.A. S. A. (72) Inventor Stephen K. Korotky, United States, 08753 New Jersey, Toms River, Shera Drive 1036 (72) Inventor John Jay. Bethelka United States, 21029 Maryland, Clarksville, Ascending Moon Pass 605 6

Claims (23)

[Claims] At least one optical channel is added / removed from a wavelength division multiplexed signal in a wavelength division multiplexing (WDM) ring network having a plurality of nodes connected via an optical fiber mechanism. In a possible add / drop arrangement, the arrangement comprises, at at least one of the plurality of nodes, a first input connected to the optical fiber arrangement for receiving the WDM signal; A first output passing through a sampled (tapped) first portion of the signal strength;
And a broadband optical coupler having a second output for passing a second portion of the optical signal strength of the WDM signal to the WDM ring network; a receiver connected to the first output; It is possible to extract at least one optical channel from the tapped first part; and a transmitter connected to a second input of the broadband optical coupler, wherein the transmitter is to be added to the WDM signal And providing at least one of the plurality of nodes substantially no interference between the optical channels carried in the WDM ring network. Means for preventing recirculation of the optical channel for the purpose of reduction; 2. The addition / deletion arrangement according to claim 1, wherein said recirculation prevention means is a wavelength suppression element. 3. The arrangement according to claim 1, wherein said recirculation preventing means is a wavelength conversion element. 4. The wavelength suppressing element functions to terminate the selected optical channel when the selected optical channel has already passed a node from which the selected optical channel is to be extracted. 3. The addition / deletion arrangement according to claim 2, wherein: 5. The method according to claim 1, wherein the wavelength conversion element passes through a node having the wavelength conversion element before a selected optical channel having the first wavelength passes through a node from which the selected optical channel is to be extracted. The addition / deletion arrangement of claim 3, operable to convert the first wavelength of the selected optical channel to a second wavelength. 6. A node having the wavelength suppressing element and the wavelength conversion element is a central node, and the central node further includes at least one optical device having an input and a plurality of outputs connected to the optical fiber mechanism. Multiplexer;
Wherein the at least one optical demultiplexer separates the WDM signal into individual optical channels; and at least one optical multiplexer having a plurality of inputs; wherein the at least one optical multiplexer comprises the individual Combining the optical channel of the at least one optical demultiplexer with the selected output of the at least one optical demultiplexer and providing the composite WDM signal to the optical fiber arrangement. 4. The method according to claim 3, wherein the wavelength suppressing element is connected to a selected input of one of the optical multiplexers, and the wavelength suppressing element is connected to a selected output of the at least one optical demultiplexer. Addition / deletion arrangement of description. 7. The method of claim 6, wherein said central node further comprises a broadband optical coupler, receiver and transmitter according to claim 1.
Delete placement. 8. The network topology wherein the WDM ring network is selected from the group consisting of a unidirectional path switching network, a unidirectional line switching ring, a two-fiber bidirectional line switching ring, and a four-fiber bidirectional line switching ring. The addition / deletion arrangement according to claim 1, wherein the addition / deletion arrangement is arranged to have: 9. A method for adding / removing at least one optical channel of a WDM signal in a wavelength division multiplexing (WDM) ring system including a plurality of nodes connected via an optical fiber mechanism, the light carrying traffic. A channel is communicated from a first node to a second node, wherein the method taps off a portion of the optical signal strength of the WDM signal using a broadband optical coupler at the second node, the tap off of the WDM signal Extracting the optical channel carrying the traffic from the extracted portion, and providing an optical channel to be added to the WDM signal via the broadband optical coupler; and
Preventing, at a central node, recirculation of the optical channels carrying traffic in the WDM ring system; thereby substantially reducing interference between optical channels in the WDM signal. How to add / remove. 10. The method of claim 9, wherein the step of preventing recirculation includes the step of substantially suppressing a remaining portion of the optical signal strength in the optical channel extracted at the second node. How to add / delete descriptions. 11. The method according to claim 11, wherein the step of preventing recirculation comprises: if the selected optical channel having a first wavelength passes through the central node before passing through the second node, the selected optical channel having the first wavelength. 10. The method according to claim 9, further comprising the step of converting the optical channel from the first wavelength to the second wavelength. 12. A wavelength division multiplexing ring system having a central node and a plurality of ring nodes connected via an optical fiber arrangement, the system further comprising: a ring node in one of the plurality of ring nodes. ,
A first input connected to the optical fiber mechanism for receiving the wavelength division multiplexed signal having a plurality of optical channels, an additional path for receiving an optical channel to be added to the wavelength division multiplexed signal; A second input connected to a first output connected to a delete path for the purpose of providing the wavelength division multiplexed signal at a first optical signal strength level such that at least one channel can be deleted from the WDM signal;
A broadband optical coupler having the wavelength division multiplexed signal having a second optical signal strength level and a second output connected to the optical fiber arrangement for providing both the added optical channel; and At the central node,
Means for preventing recirculation of optical channels for the purpose of substantially reducing interference between optical channels transmitted in the WDM ring network. 13. The communication system according to claim 12, wherein said recirculation prevention means includes a wavelength suppression element. 14. The communication system according to claim 13, wherein said means for preventing recirculation includes a wavelength conversion element. 15. The wavelength suppressing element functions to terminate the selected optical channel when the selected optical channel has already passed through a node from which the selected optical channel is to be extracted. 2. The method according to claim 1, wherein
4. The communication system according to 3. 16. The method as claimed in claim 16, wherein the wavelength converting element is configured to pass the selected optical channel having the first wavelength through the central node before passing through a node from which the selected optical channel is to be extracted. The communication system according to claim 14, operable to convert the first wavelength of the optical channel to a second wavelength. 17. Addition / addition of at least one optical channel comprising a wavelength division multiplexed (WDM) signal in a unidirectional path switching ring network having a plurality of nodes connected via a working optical fiber and a protection optical fiber. In the method for removing, the WDM signal is transmitted from a first node to a second node on both the working optical fiber and the protection optical fiber, and the method includes, at the first node, traffic for the second node. Bridging a serving optical channel to each of the working optical fiber and the protection optical fiber; at the second node, an optical signal of the WDM signal from each of the working optical fiber and the protection optical fiber using a broadband optical coupler. Tapping off part of the intensity, said working Optically filtering the traffic-carrying optical channel from the tapped-off portion of the WDM signal in each of the optical fiber and the protection optical fiber; and filtering the filtered light from the working optical fiber and the protection optical fiber. Selecting one of the channels, dropping the selected optical channel, and the WDM through the broadband optical coupler.
Providing an optical channel to be added to the signal. 18. Addition / addition of at least one optical channel comprising a wavelength division multiplexed (WDM) signal in a unidirectional line switched ring network having a plurality of nodes connected via a working optical fiber and a protection optical fiber. In the deleting method, an optical channel carrying traffic is transmitted as a WDM signal from a first node to a second node, and when the method operates normally, the WDM signal is transmitted.
Routing a signal from the first node to the second node on the working optical fiber; if a failure exists in the ring network, implement a loopback exchange at a node adjacent to the failure; Routing the WDM signal from a node to the second node using both the working optical fiber and the protection optical fiber; and the working optical fiber transmitting the WDM signal at the second node. And W from any of the protective optical fibers.
Tapping off a portion of the optical signal strength of the DM signal using a broadband optical coupler, extracting the optical channel carrying the traffic from the tapped off portion of the WDM signal, and using the broadband optical coupler. Supplying an optical channel to be added to the WDM signal through the WDM signal. 19. A wavelength division multiplexing (WD) network in a bidirectional line switched ring network having a plurality of nodes connected via a first optical fiber and a second optical fiber.
M) Add at least one optical channel consisting of signals /
In the removing method, the first and second optical fibers each have a working band and a guard band, and the W
A DM signal is transmitted from a first node to a second node, and when the method operates normally, the WDM signal is transmitted from the first node to the second node in the working band of the first optical fiber. Routing, if there is a failure in the ring network, implementing a loopback exchange at a node adjacent to the failure and transmitting the working bandwidth of the first optical fiber from the first node to the second node. Routing the WDM signal using both the guard band of the second optical fiber and the working band transmitting the WDM signal using a broadband optical coupler at the second node. Tapping off a portion of the optical signal strength of the WDM signal from any of the guard bands;
Extracting a traffic-carrying optical channel from the tapped-off portion of the signal; and providing an optical channel to be added to the WDM signal using the broadband optical coupler. / How to delete. 20. The method further comprises, at a central node, setting the wavelength of the optical channel carrying the traffic to the first wavelength if the optical channel carrying the traffic passes through the central node before passing through the second node. 20. The adding / deleting method according to claim 17, 18 or 19, further comprising: converting a wavelength to a second wavelength. 21. The method further comprises, at a central node, substantially reducing the remaining portion of the optical signal strength of the traffic-carrying optical channel if the traffic-carrying optical channel has already passed through the second node. 20. The method according to claim 17, 18 or 19, further comprising the step of: suppressing recirculation of the optical channel carrying the traffic in the ring network. . 22. A first optical fiber in a clockwise working path, a second optical fiber in a counterclockwise working path, a third optical fiber in a clockwise protection path,
Wavelength division multiplexing (WDM) in a bidirectional line-switched ring network having a plurality of nodes connected via a fourth optical fiber in a protection path in a counterclockwise direction
A method for adding / removing at least one optical channel comprising a signal, wherein the first and second optical fibers each have an open segment, wherein the WDM signal is transmitted from a first node to a second node; Routing the WDM signal from the first node to the second node on one of the first optical fiber and the second optical fiber during normal operation; If there is, realize a loopback exchange in the node adjacent to the failure, the combination of the first optical fiber and the fourth optical fiber or the combination of the second optical fiber and the third optical fiber WDM using any active
Routing a signal from the first node to the second node; and at the second node, the W
Tapping off a portion of the optical signal strength of the WDM signal from any of the optical fibers carrying the DM signal using a broadband optical coupler, and providing an optical channel carrying traffic from the tapped off portion of the WDM signal. Extracting and supplying an optical channel to be added to the WDM signal using the broadband optical coupler. 23. The method further comprises: if the optical channel carrying the traffic has already passed through the second node, the remaining portion of the optical signal strength of the optical channel carrying the traffic is transmitted to the first optical fiber and the optical fiber. 23. The method of claim 22, further comprising: routing to an open element of one of the second optical fibers; thereby preventing recirculation of the traffic-carrying optical channel in the ring network. How to add / delete descriptions.